1. Third Sunday in June, co-celebrated with but not to be confused with Father's Day, reserved for sperm donors, sometimes also called Baby Daddys, who fail to recognize or acknowledge their offspring;

2. Third Sunday in June, co-celebrated with but not to be confused with Father's Day, reserved for deadbeat dads, sometimes also called Baby Daddys;

3. Third Sunday in June, co-celebrated with but not to be confused with Father's Day, reserved for men with children after an acrimonious divorce.

"Mommy, you know how you call the sperm donor a motherfucker? Can we get him a gift?" "Gift for what son, Motherfucker's Day?"

"Mommy should we get daddy a gift?" "Don't call him Daddy. You ain't seen him in 3 years. You 8 years old and that motherfucker is 7 years behind in his child support? For what, Motherfucker's Day?"